tidb db/table name is accent-Insensitive

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)
```
mysql> create database test1;
Query OK, 0 rows affected (0.04 sec)

mysql> create table test1.café (id int);
Query OK, 0 rows affected (0.02 sec)

mysql> create table test1.cafe (id int);
Query OK, 0 rows affected (0.02 sec)

mysql>
mysql> create user newroot;
Query OK, 0 rows affected (0.02 sec)

mysql> grant insert on test1.café to newroot;
Query OK, 0 rows affected (0.01 sec)

mysql> grant insert on test1.cafe to newroot;
Query OK, 0 rows affected (0.01 sec)

mysql> select * from mysql.tables_priv;
+------+-------+---------+------------+---------+---------------------+------------+-------------+
| Host | DB | User | Table_name | Grantor | Timestamp | Table_priv | Column_priv |
+------+-------+---------+------------+---------+---------------------+------------+-------------+
| % | test1 | newroot | café | root@% | 2025-11-21 12:45:27 | Insert | Insert |
+------+-------+---------+------------+---------+---------------------+------------+-------------+
1 row in set (0.00 sec)
```

### 2. What did you expect to see? (Required)
the insert privilege of table `test.cafe` should be granted for user `newroot`.
### 3. What did you see instead (Required)
the insert privilege of table `test.café` is granted for user `newroot` instead.
### 4. What is your TiDB version? (Required)
v7.5.6